Pest Of The Month: Wireworms

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Wireworms

Identification

Wireworms, the larval stage of the click beetle, often cause severe damage to numerous crops in Florida. At least 12 species of wireworms have been found in Florida. The southern potato wireworm and tobacco wireworm are distributed throughout the southeastern U.S., but it is primarily the corn wireworm that causes significant economic damage to corn and other crops in South Florida.

Wireworms are soil pests that attack the underground portions of crops. In Florida, they have traditionally been a more important pest problem in crops grown on muck soil than on sandy soil.

The adult click beetles range from light to dark-brown with tan legs. Adults are nocturnal and hide under organic material during the day.

The larvae resemble mealworms and are slender, elongated, and yellowish brown with smooth, tough skin resembling a jointed piece of stiff wire. The body is usually cylindrical, but flat on the lower side. There are six short legs close together near the head, and the tip of the abdomen bears a flattened plate with a pair of short hooks.

Damage is caused primarily by the larvae feeding on roots, stems, tubers, and seeds of plants that are in contact with the soil. The larvae may cause considerable damage to irrigation systems by eating holes in plastic materials. Wireworms will also attack young plants, resulting in weakened plants or a reduced stand. Often, the wireworm will be found near the damaged or missing seed or plant. Damage is most likely to occur where corn is planted into a field formerly in sugar cane, pasture, or weedy fallow.

Management

Although there are a small number of insect parasites that attack wireworms, biological control of wireworms in South Florida by beneficial insects and diseases is considered to be insignificant. Birds such as the cattle egret may sometimes be of value in reducing wireworm levels because they may consume wireworms that are exposed at the surface of the soil when a field is disked or cultivated.

Cultural control practices include cover crops, crop rotation, flooding, and host plant resistance. Detection of wireworm larvae in the soil may be accomplished by baiting.

If wireworms have been a serious problem in the past, a preventive seed treatment or use of soil-applied insecticides at planting may be necessary to prevent damage to young plants by wireworm larvae.       

Gene McAvoy is a UF/IFAS Hendry County Extension agent based in LaBelle, FL.

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